ST_AsWKT method for type ST

geometry-expression.ST_AsWKT([ format])

Name	Type	Description
format	VARCHAR(128)	A string defining the output text format to use when converting the geometry-expression to WKT. If not specified, the format string defaults to 'WKT'.

LONG VARCHAR Returns the WKT representation of the geometry-expression.

The ST_AsWKT method returns a text string representing the geometry. A number of different text formats are supported (with associated options) and the desired format is selected using the optional format parameter.

The format string defines an output format and parameters to the format. The format string has one of the following formats:

format-name

format-name(parameter1=value1;parameter2=value2;...)

parameter1=value1;parameter2=value2;...

The first format specifies the format name and no parameters. All format parameters use their default values. The second format specifies the format name and a list of named parameter values. Parameters that are not supplied use their default values. The last format specifies only parameter values, and the format name defaults to 'WKT'.

The following format names may be used:

WKT The Well Known Text format defined by SQL/MM and the OGC.
EWKT The Extended Well Known Text format defined by PostGIS. This format includes the geometry's SRID and it differs from WKT in the way it represents Z and M values.

The following format parameters can be specified:

Format Name	Parameter Name	Default Value	Allowed Values	Description
WKT	Version	1.2	1.1 The WKT defined by OGC SFS 1.1. This format does not contain Z and M values. If the geometry contains Z or M values, they are removed in the output. 1.2 The WKT defined by OGC SFS 1.2. This matches version 1.1 on 2D data and extends the format to support Z and M values. PostGIS The WKT format used by some other vendors; Z and M values are included in a fashion that does not match OGC 1.2.	The Version parameter controls the version of the WKT specification used.

Note

By default, ST_AsWKT uses the original format for a geometry, if it is available. Otherwise, the internal format is used. For more information about internal and original formats, see STORAGE FORMAT clause, CREATE SPATIAL REFERENCE SYSTEM statement.

SQL/MM (ISO/IEC 13249-3: 2006) Vendor extension

The following example returns the result SRID=0;Polygon ((3 3, 8 3, 4 8, 3 3)).

SELECT Shape.ST_AsWKT( 'EWKT' ) FROM SpatialShapes WHERE ShapeID = 22

ST_AsWKT method for type ST_Geometry

Syntax

Parameters

Returns

Remarks

Note

Standards and compatibility

Example